Modified polyester fiber, etching finished woven and knitted fabric containing the fiber, and method for producing same

ABSTRACT

As a fiber for weight reduction, a modified polyester fiber, which is obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 16 mol % and equal to or less than 25 mol % of an aliphatic dicarboxylic acid having equal to or more than 4 and equal to or less than 8 carbon atoms; and equal to or more than 2 mol % and equal to or less than 5 mol % of a metal sulfonate group-containing aromatic dicarboxylic acid, is used. This modified polyester fiber has a single fiber fineness of equal to or more than 0.6 dtex and equal to or less than 3.5 dtex. A mixed woven or knitted fabric composed of two or more types of fibers, which are the modified polyester fiber, a regular polyester fiber, and optionally, a polyurethane fiber, is capable of exhibiting good etching finish properties by using an etching finish agent that contains an etching finish accelerator, for example, a Mei printer OP-2 (manufactured by Meisei Chemical Works, Ltd.) and sodium carbonate, and also exhibits low reduction in strength of non-etching finished parts.

TECHNICAL FIELD

The invention relates to an easily alkali soluble polyester fiber havinghigh etching finish properties, etching finished woven and knittedfabrics which contain said fiber and a method for producing the wovenand knitted fabrics.

BACKGROUND ART

In general, etching finishing which includes: printing an etching pasteon a woven or knitted fabric composed of two or more types of fibersincluding a fiber having high etching finish properties and a fiber hardto be etched in a patterned manner; and embrittling and removing thefiber having high etching finish properties; is also called opalfinishing. The etching finishing has been widely known as processing forforming a watermark pattern or a highly stretchable part. A chemicalreaction in the etching finishing varies depending on types of fibers.For example, a method for removing a polyester fiber is also referred toas alkali weight reduction. The method is alkaline hydrolysis which usessodium hydroxide, potassium hydroxide and the like. On the other hand,in order to remove a cellulosic fiber such as cotton and acetate, acidhydrolysis, dissolution by carbonization or a hot organic solvent andthe like have been utilized.

As etching finishing for a woven or knitted fabric made of a polyesterfiber, a method which includes: printing an etching paste on a woven orknitted fabric composed of a modified polyester fiber having highetching finish properties and an unmodified polyester fiber having lowetching finish properties in a patterned manner; and removing themodified polyester fiber having high etching finish properties; has beenknown. As such a method, a method which includes: printing a pasteliquid containing sodium hydroxide or potassium hydroxide as an etchingfinish agent; and performing heat treatment; has been known.

However, the method, which uses sodium hydroxide or potassium hydroxidewhen performing etching finishing by utilizing a difference inhydrolyzability between the modified polyester fiber having high etchingfinish properties and the unmodified polyester fiber having low etchingfinish properties, may even embrittle the unmodified polyester fiber.Accordingly, the method has a problem which may cause reduction instrength and etching defect. In addition, sodium hydroxide and potassiumhydroxide are strong alkaline substances, and therefore, they have hightoxicity and irritancy to human, and also have high influence on aquaticenvironment.

On the other hand, in order to improve dyeability of a polyethyleneterephthalate fiber, which has been dyed under high temperature and highpressure by a disperse dye, such that the fiber is capable of being dyedby dyeing under normal pressure by using a disperse dye and a cationicdye, a modified polyester fiber which is obtained by copolymerizing apolyethylene terephthalate with 0.4 to 5 mol % of 5-sodiumsulfoisophthalic acid and 2 to 15 mol % of adipic acid has been known,for example, by JP S61-239015 A (Patent Document 1), JP H08-269820 A(Patent Document 2), JP 2013-18802 A (Patent Document 3) and the like.

Such a modified polyester fiber has been diversified from the point ofview of dyeing, because types of dyes which can be applied to the fiberincrease. In addition, the modified polyester fiber has been also usedfor combined use of a polyethylene terephthalate fiber having highchemical resistance and a fiber having low chemical resistance in opalfinishing. However, a conventional modified polyester fiber has been notsufficiently satisfied yet in terms of etching removal properties by analkali when performing opal finishing. Accordingly, a modified polyesterfiber, which maintains physical properties of the fiber as much aspossible and which is etching removed more easily, has been required inorder to diversify opal finished products.

In addition, for example, according to JP 2000-096439 A (Patent Document4), with regard to etching finishing of a modified polyester fiber in awoven or knitted fabric in which a fabric is composed of the modifiedpolyester fiber and an unmodified polyester fiber, etching finishingwhich uses an etching finish agent containing guanidine carbonate hasbeen proposed. However, etching finishing by using guanidine carbonateis good in etching finish properties of the modified polyester, butthere has been a problem that the unmodified polyester tends toembrittle, which causes the reduction in strength.

Further, according to JP 2000-282377 A (Patent Document 5), in etchingfinishing of a modified polyester fiber in a woven or knitted fabricwhich contains an normal pressure cation-dyeable polyester fiber as anessential component, a method which includes: printing a paste liquidcontaining a quaternary ammonium salt; performing heat treatment; andafter that, performing alkali weight reduction to remove the modifiedpolyester fiber; has been proposed. However, since the method is alkaliweight reduction processing which uses sodium hydroxide, there has beena problem that strength of the modified polyester fiber and anunmodified polyester fiber cannot be maintained.

Furthermore, for example, according to JP 2008-038332 A (Patent Document6), in etching finishing of a modified polyester fiber in a woven orknitted fabric composed of the modified polyester fiber and anunmodified polyester fiber, it has been proposed to perform etchingfinishing by a method which includes making an etching finish agentcontaining at least one of guanidine carbonate, sodium hydroxide, andpotassium hydroxide adhere to the fabric by inkjet textile printing. Inthe method, etching finishing is performed by controlling an adhesionamount of the etching finish agent by inkjet textile printing. However,in order to maintain strength of the unmodified polyester fiber,fineness of the unmodified polyester fiber has been made larger.Alternatively, a bicomponent filament yarn in which a core part is anunmodified polyester fiber and a sheath part is a modified polyesterfiber has been used such that the etching finish agent adheres only tothe modified polyester fiber, or other methods have been used. In anycase, there has been a problem that embrittlement of the unmodifiedpolyester fiber cannot be prevented.

In addition, for example, according to WO 2007/086593 A (Patent Document7), a method in which a fabric to which etching finishing is performedis composed of a non-elastic fiber and an elastic fiber has beenproposed. In the fabric, a cation dyeable polyester fiber, which is afiber capable of being etched, and a nylon fiber, which is a fiber notcapable of being etched, are used as the non-elastic fiber, and anether-based polyurethane fiber is used as the elastic fiber. There hasbeen a problem that the cation dyeable polyester fiber and thepolyurethane fiber, which are not the subjects of etching tend to beetched when sodium hydroxide is used as the etching finish agent, whichcauses reduction in elasticity and strength.

CITATION LIST Patent Document

-   Patent Document 1: JP S61-239015 A-   Patent Document 2: JP H08-269820 A-   Patent Document 3: JP 2013-18802 A-   Patent Document 4: JP 2000-096439 A-   Patent Document 5: JP 2000-282377 A-   Patent Document 6: JP 2008-038332 A-   Patent Document 7: WO 2007/086593 A

SUMMARY OF INVENTION Technical Problem

One object of the invention is to provide an easily alkali solublemodified polyester fiber which is used as a fiber having low chemicalresistance in opal finishing and is capable of being easilyetching-removed by an alkali. Conventionally, an aliphatic dicarboxylicacid and a metal sulfonate group-containing aromatic dicarboxylic acidare copolymer components which are known to have modifying effects ofdyeability of a polyethylene terephthalate fiber. However, it is foundthat when specific amounts of the aliphatic dicarboxylic acid and themetal sulfonate group-containing aromatic dicarboxylic acid are used,the modifying effects of dyeability are maintained, and further, it isfound that an easily alkali soluble fiber, which can be easilyetching-removed, can be obtained, and thus the invention has beencompleted.

In addition, as described above, there has been a problem that inetching finishing which includes etching a modified polyester fiber,sufficient etching can be achieved only in the case when a strong alkaliis used. On the contrary, when the strong alkali is used, there has beena problem that strength of a fabric which has been subjected to etchingfinishing tends to decrease. In view of this situation, another objectof the invention is to provide etching finished woven and knittedfabrics having high etching finish properties, which can be easilyetched even when a weak alkali is used, by using a modified polyesterfiber having sufficient etching finish properties, while preventingreduction in strength of fibers in parts containing an unmodifiedpolyester fiber other than etched parts. In addition, another object ofthe invention is to provide a method for producing the etching finishedwoven and knitted fabrics.

Solution to Problem

In conventional technologies, in etching finishing of a woven or knittedfabric composed of a modified polyester fiber and an unmodifiedpolyester fiber, in order to prevent the unmodified polyester fiber frombeing embrittled, a method which includes: printing an alkali weightreduction accelerator without using a strong alkaline substance such assodium hydroxide and potassium hydroxide in an etching paste; performingheat treatment; and promoting alkali weight reduction of printed partsat the time of the alkali weight reduction after the printing and theheat treatment; has been considered. However, the inventors have focusedon further modification of a modified polyester fiber, and haveconducted various studies and experiments. As a result, the inventorshave found that alkali weight reduction of a certain modified polyesterfiber can be performed in a certain pH range, without using a strongalkaline substance such as sodium hydroxide and potassium hydroxide, andwithout an influence of reduction in strength of an unmodified polyesterfiber and a polyurethane fiber. The inventors have found that the alkaliweight reduction only of the modified polyester fiber can be achieved.

The modified polyester fiber according to the invention is a modifiedpolyester fiber characterized by having a weight reduction ratio ofequal to or more than 5% and equal to or less than 15%, the weightreduction ratio being obtained by the following measuring method:

<Measuring Method of Weight Reduction Ratio of Fiber>

the measuring method of the weight reduction ratio including adding 100g of a fiber to 2 L of an aqueous solution including 40 g/L of sodiumcarbonate; heating an obtained mixture at 100° C. for 30 minutes;performing drying treatment at 80° C. for 60 minutes; and after that,measuring a fiber mass A g.

weight reduction ratio (%)={(100−A)/100}×100

It is preferable that the modified polyester fiber according to theinvention is characterized in that the modified polyester fiber iscomposed of a modified polyester obtained by copolymerizing: ethyleneterephthalate as a main constitutional unit; equal to or more than 12mol % and equal to or less than 25 mol % of an aliphatic dicarboxylicacid having 4 to 8 carbon atoms; and equal to or more than 2 mol % andequal to or less than 5 mol % of a metal sulfonate group-containingaromatic dicarboxylic acid.

It is preferable that the modified polyester fiber according to theinvention is characterized in that the aliphatic dicarboxylic acid isadipic acid, and the metal sulfonate group-containing aromaticdicarboxylic acid is 5-sodium sulfoisophthalic acid.

It is preferable that the modified polyester fiber according to theinvention is characterized by having a content of diethylene glycol ofequal to or more than 0.5 mass % and equal to or less than 3.0 mass %.

It is preferable that the modified polyester fiber according to theinvention has a single fiber fineness of equal to or more than 0.6 dtexand equal to or less than 3.5 dtex, a fiber strength of equal to or morethan 2.0 cN/dtex and equal to or less than 3.5 cN/dtex, and a fiberelongation of equal to or more than 25% and equal to or less than 45%.

It is preferable that the modified polyester fiber according to theinvention is characterized in that the modified polyester fiber containslithium acetate and diethylene glycol, and a content of the lithiumacetate is 50 to 120 ppm in terms of lithium atom content.

The woven or knitted fabric according to the invention contains amodified polyester fiber and a fiber not for weight reduction,characterized in that: the modified polyester fiber has a weightreduction ratio of equal to or more than 5% and equal to or less than15% and the fiber not for weight reduction has a weight reduction ratioof equal to or more than 0% and less than 5%; a content of the modifiedpolyester fiber in the woven or knitted fabric is equal to or more than5 mass % and equal to or less than 50 mass %; a content of the fiber notfor weight reduction in the woven or knitted fabric is equal to or morethan 50 mass % and equal to or less than 95 mass %; and the weightreduction ratio is obtained by the following measuring method:

<Measuring Method of Weight Reduction Ratio of Fiber>

the measuring method of the weight reduction ratio including: adding 100g of a fiber to 2 L of an aqueous solution including 40 g/L of sodiumcarbonate; heating an obtained mixture at 100° C. for 30 minutes;performing drying treatment at 80° C. for 60 minutes; and after that,measuring a fiber mass A g.

weight reduction ratio (%)=((100−A)/100)×100

The woven or knitted fabric according to the invention contains amodified polyester fiber and a fiber not for weight reduction,characterized in that: the modified polyester fiber has a weightreduction ratio of equal to or more than 5% and equal to or less than15% and the fiber not for weight reduction has a weight reduction ratioof equal to or more than 0% and less than 5%; the woven or knittedfabric has an etching finished part of the modified polyester fiber; aweight reduction ratio of the modified polyester fiber in the etchingfinished part to the modified polyester fiber in a non-etching finishedpart is equal to or more than 50 mass % and equal to or less than 100mass %; and the weight reduction ratio is obtained by theabove-described measuring method of the weight reduction ratio of thefiber.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that a difference between said weightreduction ratio of the modified polyester fiber and said weightreduction ratio of the non-etched fiber is equal to or more than 5%.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that a burst strength of the woven orknitted fabric in the etching finished part is equal to or more than 250kPa and equal to or less than 900 kPa. It is preferable that the wovenor knitted fabric according to the invention has a strength retentionratio of a burst strength of the woven or knitted fabric in the etchingfinished part to a burst strength of the woven or knitted fabric in thenon-etching finished part of equal to or more than 50%.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that the modified polyester fiber is amodified polyester that is obtained by copolymerizing: ethyleneterephthalate as a main constitutional unit; equal to or more than 16mol % and equal to or less than 25 mol % of an aliphatic dicarboxylicacid having 4 to 8 carbon atoms; and equal to or more than 2 mol % andequal to or less than 5 mol % of a metal sulfonate group-containingaromatic dicarboxylic acid.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that the fiber not for weight reductioncontains equal to or more than 50 mass % and equal to or less than 95mass % of synthetic fibers.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that the synthetic fiber is at least oneof a regular polyester fiber, a polyamide fiber, an elastic fiber, apolyolefin fiber, and an acrylic fiber.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that a single fiber fineness of themodified polyester fiber is equal to or more than 0.6 dtex and equal toor less than 3.5 dtex.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that the elastic fiber is composed of anyone of a polyurethane fiber, a polytrimethylene terephthalate fiber, anda polybutylene terephthalate fiber.

It is preferable that the method for producing the woven or knittedfabric according to the invention includes: printing an etching finishagent on a cloth that contains a modified polyester fiber having aweight reduction ratio of equal to or more than 5% and equal to or lessthan 15% and a fiber not for weight reduction; and performing weightreduction processing by supplying a superheated steam to a part on whichthe etching finish agent is printed; the method being characterized inthat: the etching finish agent has a pH of equal to or more than 8 andequal to or less than 13; the heating method includes supplying asuperheated steam of equal to or higher than 150° C. and equal to orlower than 200° C.; the heating time is equal to or more than 5 minutesand equal to or less than 15 minutes; and the weight reduction ratio isobtained by the above-described measuring method of the weight reductionratio of the fiber.

Advantageous Effects of Invention

According to the invention, in etching finishing of a woven or knittedfabric containing a modified polyester fiber, it is possible thatreduction in strength of parts other than etched parts of the modifiedpolyester fiber does not occur. In addition, it is possible thatreduction in strength of etched parts of the woven or knitted fabriccontaining a fiber other than the modified polyester fiber does notoccur. At the same time, a good etching action can be obtained.According to the invention, it is possible to obtain an etching finishedproduct of which the modified polyester fiber is etched well withoutcausing reduction in strength.

DESCRIPTION OF EMBODIMENTS

The modified polyester fiber according to the invention is a modifiedpolyester fiber characterized by having a weight reduction ratio ofequal to or more than 5% and equal to or less than 15%, the weightreduction ratio being obtained by the following measuring method:

<Measuring Method of Weight Reduction Ratio of Fiber>

the measuring method of the weight reduction ratio including: adding 100g of a fiber to 2 L of an aqueous solution including 40 g/L of sodiumcarbonate; heating an obtained mixture at 100° C. for 30 minutes;performing drying treatment at 80° C. for 60 minutes; and after that,measuring a fiber mass A g.

weight reduction ratio (%)={(100−A)/100}×100

When the modified polyester fiber according to the invention has theweight reduction ratio of equal to or more than 5%, weight-reduction ofthe modified polyester fiber is capable of being performed with analkali easily, and deterioration in physical properties of a fiber notfor weight reduction can be suppressed. In addition, when the weightreduction ratio is equal to or less than 15%, reduction in strength ofthe modified polyester fiber according to the invention is low, and itis possible to suppress thread breakage in a production process of awoven or knitted fabric.

From the above points of view, the weight reduction ratio of the fiberis more preferably equal to or more than 7% and equal to or less than13%, and is even more preferably equal to or more than 8% and equal toor less than 11%.

It is preferable that the modified polyester fiber according to theinvention is composed of a modified polyester obtained bycopolymerizing: ethylene terephthalate as a main constitutional unit;equal to or more than 12 mol % and equal to or less than 25 mol % of analiphatic dicarboxylic acid having 4 to 8 carbon atoms; and equal to ormore than 2 mol % and equal to or less than 5 mol % of a metal sulfonategroup-containing aromatic dicarboxylic acid.

It is preferable that the modified polyester fiber according to theinvention is characterized in that the aliphatic dicarboxylic acid isadipic acid, and the metal sulfonate group-containing aromaticdicarboxylic acid is 5-sodium sulfoisophthalic acid.

The aliphatic dicarboxylic acid having 4 to 8 carbon atoms, which is acopolymer component, increases alkali solubility of the polyester fiberby disturbing an amorphous structure of the fiber. Examples of thealiphatic dicarboxylic acid having 4 to 8 carbon atoms include succinicacid, glutaric acid, adipic acid, pimelic acid, and suberic acid, andparticularly preferable examples of the aliphatic dicarboxylic acidhaving 4 to 8 carbon atoms include adipic acid.

An amount of the copolymerized aliphatic dicarboxylic acid having 4 to 8carbon atoms is equal to or more than 16 mol % and equal to or less than25 mol %, and is preferably, equal to or more than 18 mol % and equal toor less than 20 mol %. When the amount of the copolymerized aliphaticdicarboxylic acid having 4 to 8 carbon atoms is within this range,significant deterioration in dynamic and heat characteristics issuppressed, and the amorphous structure of the fiber is disturbed, whichcontributes to improvement of dyeability with a disperse dye and acationic dye. In addition, alkali solubility of the fiber issignificantly increased. When the amount of the copolymerized aliphaticdicarboxylic acid having 4 to 8 carbon atoms is equal to or more than 16mol %, it becomes easy to obtain a solubility with an alkali easilysuitable for opal finishing. When the amount of the copolymerizedaliphatic dicarboxylic acid having 4 to 8 carbon atoms is equal to orless than 25 mol %, it becomes easy to maintain physical properties,fastness properties, and heat characteristics such as heat resistance ofthe fiber, which are required to be used as a fiber.

The metal sulfonate group-containing aromatic dicarboxylic acid, whichis the other copolymer component, is a component which acts as acationic dye-dyeing site since a metal sulfonate group is introducedinto a fiber. In addition, the metal sulfonate group-containing aromaticdicarboxylic acid is a component which makes it possible to dye apolyethylene terephthalate fiber with a cationic dye under normalpressure. Further, the metal sulfonate group, together with an aromaticring, is introduced into the fiber, and makes it possible to improvedyeability with a disperse dye. Furthermore, the temperature on dyingcan be lowered. In addition, the metal sulfonate group-containingaromatic dicarboxylic acid also contributes to improvement of alkalisolubility of the fiber. Examples of the metal sulfonategroup-containing aromatic dicarboxylic acid include, 5-sodiumsulfoisophthalic acid, potassium sulfoterephthalic acid, sodiumsulfonaphthalene dicarboxylic acid and the like. Particularly preferableexamples of the metal sulfonate group-containing aromatic dicarboxylicacid include 5-sodium sulfoisophthalic acid.

An amount of the copolymerized metal sulfonate group-containing aromaticdicarboxylic acid is equal to or more than 2 mol % and equal to or lessthan 5 mol %. When the amount of the copolymerized metal sulfonategroup-containing aromatic dicarboxylic acid is equal to or more than 2mol %, it becomes easy to obtain sufficient dyeability with a cationicdye. In addition, it tends to be easy to lower a temperature on dyingwith a disperse dye sufficiently. When the amount of the copolymerizedmetal sulfonate group-containing aromatic dicarboxylic acid is equal toor less than 5 mol %, it tends to be easy to decrease the threadbreakage during spinning and the occurrence of fuzz.

The production of the modified polyester according to the invention canbe achieved by a known method which is the same as the production of apolyethylene terephthalate. In other words, when terephthalic acid isused, a method which includes causing an esterification reaction ofterephthalic acid with ethylene glycol is employed. Alternatively, whendimethyl terephthalate, which is an ester, is used, a method whichincludes causing a transesterification reaction between dimethylterephthalate and ethylene glycol, and thereafter, performing apolycondensation reaction is employed.

The aliphatic dicarboxylic acid having 4 to 8 carbon atoms, which is acopolymer component, can be added at an arbitrary stage beforecompletion of the polycondensation. For example, the aliphaticdicarboxylic acid having 4 to 8 carbon atoms is added as a slurry inethylene glycol at the time of starting the esterification reactionbetween terephthalic acid and ethylene glycol. Alternatively, thealiphatic dicarboxylic acid having 4 to 8 carbon atoms is added as adispersion or a solution of the aliphatic dicarboxylic acid orbis-hydroxy dicarbonate in ethylene glycol tobis(β-hydroxyethyl)terephthalate which is generated by theesterification reaction between terephthalic acid and ethylene glycol.Meanwhile, when producing the modified polyester, a gloss reducingagent, an antistatic agent, a flame retardant, a pigment and the likemay be added at an arbitrary stage before completion of thepolycondensation.

Similarly, the metal sulfonate group-containing aromatic dicarboxylicacid, which is a copolymer component in producing the modifiedpolyester, can be added at an arbitrary stage before completion of thepolycondensation.

For example, the metal sulfonate group-containing aromatic dicarboxylicacid is added as a slurry in ethyleneglycol at the time of starting theesterification reaction between terephthalic acid and ethylene glycol.Alternatively, the metal sulfonate group-containing aromaticdicarboxylic acid is added as a dispersion or a solution of the metalsulfonate group-containing aromatic dicarboxylic acid dimethyl ester ordiglycol ester in ethylene glycol to bis(β-hydroxyethyl)terephthalatewhich is generated by the esterification reaction between terephthalicacid and ethylene glycol.

It is preferable that the modified polyester fiber according to theinvention has a content of diethylene glycol of equal to or more than0.5 mass % and equal to or less than 3.0 mass %.

When producing the modified polyester, especially when producing themodified polyester by a direct esterification method, diethylene glycol,which is produced by dehydrative dimerization of ethylene glycol, isproduced as a by-product, and remains in the subsequent polycondensationreaction system.

When the content of diethylene glycol in the modified polyester fiberaccording to the invention is equal to or less than 3.0 mass %,deterioration in a fiber strength can be suppressed. From the abovepoints of view, the content of diethylene glycol in the modifiedpolyester fiber is more preferably equal to or less than 2.5 mass %, andis further more preferably equal to or less than 2.0 mass %.

Preferable examples of the method for suppressing the by-production ofdiethylene glycol include a method which includes adding a weak acidsalt or a hydroxide of an alkali metal or an alkali earth metal to thereaction system during the esterification reaction. In particular,sodium hydroxide, sodium acetate, lithium acetate and the like areeffective for suppressing the by-production of diethylene glycol, andare preferably used when the content of dicarboxylic acids, which arecopolymer components, is equal to or more than 10 mol %. In theinvention, lithium acetate is more preferably used.

It is preferable that the modified polyester fiber according to theinvention contains lithium acetate and a content of the lithium acetateis 50 to 120 ppm in terms of lithium atom content.

The content of lithium acetate is preferably 50 to 150 ppm to a polymercomposition in terms of lithium atom content, is more preferably 100 to150 ppm, and is even more preferably 120 to 150 ppm. When such an amountof lithium acetate is added and contained, the modified polyester havinga content of ethylene glycol of equal to or more than 0.5 mass % andequal to or less than 3.0 mass % can be obtained.

It is preferable that the modified polyester fiber according to theinvention has a single fiber fineness of equal to or more than 0.6 dtexand equal to or less than 3.5 dtex, a fiber strength of equal to or morethan 2 cN/dtex and equal to or less than 3.5 cN/dtex, and a fiberelongation of equal to or more than 25% and equal to or less than 45%.

It is preferable that the modified polyester fiber according to theinvention has a single fiber fineness of equal to or more than 0.6 dtex,because a fiber strength can be maintained and the manufacturability ofa woven or knitted fabric is good. It is preferable that the modifiedpolyester fiber according to the invention has a single fiber finenessof equal to or less than 3.5 dtex, because the weight reductionprocessability is good. From the above points of view, the single fiberfineness is more preferably equal to or more than 1 dtex and equal to orless than 3 dtex, and is further more preferably equal to or more than1.3 dtex and equal to or less than 2.5 dtex.

It is preferable that the modified polyester fiber according to theinvention has a fiber strength of equal to or more than 2 cN/dtex andequal to or less than 3.5 cN/dtex, because there is no problem in themanufacturability of a woven or knitted fabric. It is more preferablethat the modified polyester fiber according to the invention has a fiberstrength of equal to or more than 2.3 cN/dtex and equal to or less than3 cN/dtex. In addition, it is preferable that the modified polyesterfiber according to the invention has an elongation of equal to or morethan 25% and equal to or less than 45%, because the manufacturability ofa woven or knitted fabric is good. It is more preferable that themodified polyester fiber according to the invention has an elongation ofequal to or more than 30% and equal to or less than 40%.

The modified polyester according to the invention is produced through,for example, the following production steps:

the step of supplying a slurry of terephthalic acid and ethylene glycolinto an esterification reaction vessel in whichbis(β-hydroxyethyl)terephthalate and an oligomer thereof are present,and causing an esterification reaction at a temperature around 250° C.for 3 to 8 hours to give a reaction product having an esterificationrate of equal to or more than 95%; the step of transferring theesterification reaction product to a polymerization vessel, adding eachof an aliphatic dicarboxylic acid and a metal sulfonate group-containingaromatic dicarboxylic acid, which are copolymer components, lithiumacetate, magnesium acetate, triethyl phosphate, and germanium dioxide asa solution or a dispersion in ethylene glycol, and thereafter, addingantimony trioxide, which is a polymerization catalyst, as a dispersionin ethylene glycol, raising the temperature, and performing apolycondensation reaction at a temperature around 270° C. under reducedpressure until a polycondensate reaches a predetermined limitingviscosity; and after that,

the step of removing the polycondensate to give a strand and making thestrand as a chip.

The modified polyester fiber according to the invention can be obtainedby a known melt spinning method similar to a method for producing apolyethylene terephthalate fiber. As a method for making a yarn whichincludes spinning by extruding a modified polyester chip from a spinninghole of a spinning nozzle and subsequent drawing, a known method may bealso employed. For example, for the production of the modified polyesterfiber, a condition of: a spinning temperature of 240 to 300° C.; aspinning speed of 1,000 to 2,000 m/min; a drawing temperature of 60 to90° C.; a drawing speed of 400 to 1,000 m/min; a drawing ratio of 1.8 to3.5 times; a drawing ratio of 0.65 to 0.80 times the maximum drawingratio; and a heat set temperature of 110 to 160° C.; is used. Here, themaximum drawing ratio refers to a ratio obtained when drawing isperformed until an undrawn yarn is cut at a drawing temperature of 80°C., a heat set temperature of 145° C., and a drawing speed of 600 m/min.

In a yarn manufacturing process, a method which includes winding anundrawn yarn after spinning once and then drawing, a method whichincludes drawing without winding an undrawn yarn after spinning, amethod which includes winding a yarn as a half undrawn yarn by highspeed spinning at a spinning speed of equal to or more than 2,000 m/min,a method which includes high speed spinning and drawing without winding,or a similar method may be employed.

The modified polyester fiber according to the invention is suitably usedfor opal finishing in which a part of component fibers of a woven orknitted fabric is etching removed. Accordingly, a single fiber finenessof the modified polyester fiber, or when the form of the fiber is afilament yarn, a single yarn fineness, is preferably equal to or morethan 0.6 dtex and equal to or less than 3.5 dtex because etching removalof the fiber is easy. The cross sectional shape of the modifiedpolyester fiber may be any shapes including a circular shape, a flatshape, a triangle shape, a Y-shape, a multilobed shape and the like. Inaddition, the form of the modified polyester fiber may be any of a shortfiber, and a filament. When the form of the fiber is a filament, thefilament yarn may be subjected to crimping processing or false twistprocessing.

The modified polyester fiber according to the invention has easydyeability, that is, capability of being dyed with a disperse dye undernormal pressure, as well as dyeability, that is, capability of beingdyed with a cationic dye under normal pressure. At the same time, themodified polyester fiber according to the invention has solubility withan alkali easily, that is, capability of being etching removed easily.Accordingly, when a mixed woven or knitted fabric, which is obtained bycombined weaving or knitting of the modified polyester fiber accordingto the invention with another fiber having high chemical resistance, issubjected to opal finishing, opal finished products having variouscolors and color tones can be obtained by adding a disperse dye or acationic dye to an etching paste or a paste containing an etching finishaccelerator for printing. Especially preferable examples of the fiberhaving high chemical resistance which is used in combination include apolyethylene terephthalate fiber. Accordingly, the modified polyesterfiber according to the invention is capable of producing an opalfinished product of a mixed woven or knitted fabric consisting only ofpolyester fibers, by being combined with a polyethylene terephthalatefiber. In addition, the modified polyester fiber according to theinvention may be used in combination with another fiber having lowchemical resistance or another fiber having different chemicalresistance, for example, wool, silk, cotton, rayon, an acetate fiber, apolyamide fiber or the like, other than a fiber having high chemicalresistance, according to the need. The modified polyester fiberaccording to the invention is capable of producing an opal finishedproduct having various colors, color tones, and textures, by adding adye suitable for the fiber to be combined to an etching paste.

In addition, the modified polyester fiber according to the inventionmakes it possible to obtain an opal finished product havingstretchability due to its solubility with an alkali easily. The opalfinished product having stretchability can be obtained by combining themodified polyester fiber with a polyethylene terephthalate fiber and apolyurethane fiber and performing opal finishing under a mild alkalitreatment condition such that a highly stretchable part in which onlythe modified polyester fiber is etching removed is formed withoutembrittling the polyurethane fiber. The polyurethane fiber which is usedmay be any of a polyether-based polyurethane fiber, and apolyester-based polyurethane fiber.

For opal finishing performed on a mixed woven or knitted fabric obtainedby combined weaving or knitting of the modified polyester fiberaccording to the invention with a polyethylene terephthalate fiber, andoptionally, a polyurethane fiber, for example, a method which includesthe steps of printing an etching paste which contains sodium hydroxideas an etching agent, drying, etching treating by wet heating or dryheating, and soaping and washing with water; a method which includes thesteps of printing a paste containing an etching finish accelerator,drying and heat treating, soaping and washing with water, and alkaliweight reduction treating (etching treating) with sodium hydroxide; andthe like may be employed. However, conditions of the methods varydepending on a woven or knitted fabric texture, a mixing ratio offibers, an etching pattern, a use or the like. In the case of opalfinishing of a mixed woven or knitted fabric composed of the modifiedpolyester fiber according to the invention, a polyethylene terephthalatefiber, and optionally, a polyurethane fiber, the alkali weight reductiontreatment (etching treatment) in the latter method may be performed byalkali weight reduction processing which is generally applied to a wovenor knitted fabric of a polyester fiber, and the latter method is morepreferably employed. When opal finishing is performed, a dye may beappropriately added to an etching paste or a paste containing an etchingfinish accelerator such that etching and coloring of a non-etched fiberare performed simultaneously. In addition, dying may be combinedlyperformed before or after opal finishing. As a result, an opal finishedproduct which has various colors, a low single fiber fineness, as wellas a high-grade sense can be obtained.

Examples of the opal finished product of the mixed woven or knittedfabric obtained by using the modified polyester fiber according to theinvention include an embroidery lace, an outerwear as well as aninnerwear such as lingerie, a foundation, a swimsuit, an underwear forsports, a bodysuit, a leotard, tights for sports and a girdle.

The woven or knitted fabric according to the invention is a woven orknitted fabric containing a modified polyester fiber and a fiber not forweight reduction, characterized in that: the modified polyester fiberhas a weight reduction ratio of equal to or more than 5% and equal to orless than 15% and the fiber not for weight reduction has a weightreduction ratio of equal to or more than 0% and less than 5%; a contentof the modified polyester fiber in the woven or knitted fabric is equalto or more than 5 mass % and equal to or less than 50 mass %; a contentof the fiber not for weight reduction in the woven or knitted fabric isequal to or more than 50 mass % and equal to or less than 95 mass %; andthe weight reduction ratio is obtained by the following measuringmethod:

<Measuring Method of Weight Reduction Ratio of Fiber>

the measuring method of the weight reduction ratio including: adding 100g of a fiber to 2 L of an aqueous solution including 40 g/L of sodiumcarbonate; heating an obtained mixture at 100° C. for 30 minutes;performing drying treatment at 80° C. for 60 minutes; and after that,measuring a fiber mass A g.

weight reduction ratio (%)=((100−A)/100)×100

The woven or knitted fabric according to the invention contains thefiber not for weight reduction having the weight reduction ratio ofequal to or more than 0% and less than 5%, and therefore, when themodified polyester fiber according to the invention is subjected toweight reduction with an alkali, the fiber not for weight reductionremains and etching finishing can be performed.

From the above point of view, the weight reduction ratio of the fibernot for weight reduction is more preferably equal to or less than 4%,and is further more preferably equal to or less than 3%.

In addition, when the content of the modified polyester fiber in thewoven or knitted fabric is equal to or more than 5 mass %, an effect ofetching finishing tends to be easily exhibited. Further, when thecontent of the modified polyester fiber in the woven or knitted fabricis equal to or less than 50 mass %, the non-etched fiber remainssufficiently, and therefore, strength of the woven or knitted fabric canbe maintained sufficiently.

From the above points of view, the content of the modified polyesterfiber in the woven or knitted fabric is more preferably equal to or morethan 10 mass % and equal to or less than 40 mass %, and is even morepreferably equal to or more than 15 mass % and equal to or less than 30mass %.

The woven or knitted fabric according to the invention is a woven orknitted fabric containing a modified polyester fiber and a fiber not forweight reduction, characterized in that: the modified polyester fiberhas a weight reduction ratio of equal to or more than 5% and equal to orless than 15% and the fiber not for weight reduction has a weightreduction ratio of equal to or more than 0% and less than 5%; the wovenor knitted fabric has an etching finished part of the modified polyesterfiber; a weight reduction ratio of the modified polyester fiber in theetching finished part to the modified polyester fiber in a non-etchingfinished part is equal to or more than 50 mass % and equal to or lessthan 100 mass %; and the weight reduction ratio is obtained by thefollowing measuring method:

<Measuring Method of Weight Reduction Ratio of Fiber>

the measuring method of the weight reduction ratio including: adding 100g of a fiber to 2 L of an aqueous solution including 40 g/L of sodiumcarbonate; heating an obtained mixture at 100° C. for 30 minutes;performing drying treatment at 80° C. for 60 minutes; and after that,measuring a fiber mass A g.

weight reduction ratio (%)={(100−A)/100}×100

The woven or knitted fabric according to the invention having theetching finished part has a weight reduction ratio of the modifiedpolyester fiber in the etching finished part to the modified polyesterfiber in the non-etching finished part of equal to or more than 50 mass% and equal to or less than 100 mass %.

When the weight reduction ratio is 50%, an effect of weight reductionprocessing on a woven fabric is sufficient. When the weight reductionratio is 100%, there is no modified polyester fiber in the etchingfinished part, and such a state is preferable. However, from the pointof view of a designing effect on the woven or knitted fabric, it ispreferable to make at least a part of the modified polyester remain inthe etching finished part.

It is preferable that the woven or knitted fabric according to theinvention has a burst strength of the woven or knitted fabric in theetching finished part of equal to or more than 250 kPa and equal to orless than 900 kPa.

When the burst strength is equal to or more than 250 kPa, the strengthhas no problem for the woven or knitted fabric to be used as a product.In addition, when the burst strength is 900 kPa, the strength issufficient for the woven or knitted fabric to be used.

From the above points of view, the burst strength is preferably equal toor more than 400 kPa, and is more preferably equal to or more than 600kPa.

It is preferable that the woven or knitted fabric according to theinvention has a strength retention ratio of a burst strength of thewoven or knitted fabric in the etching finished part to a burst strengthof the woven or knitted fabric in the non-etching finished part of equalto or more than 50%.

When the strength retention ratio of the burst strength of the woven orknitted fabric in the etching finished part to the burst strength of thewoven or knitted fabric in the non-etching finished part is equal to ormore than 50%, the break of the woven or knitted fabric due to theexcess stress concentration to the etching finished part is suppressed.

From the above points of view, the strength retention ratio is morepreferably equal to or more than 70%, and is further more preferablyequal to or more than 85%.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that the modified polyester fiber is amodified polyester fiber that is obtained by copolymerizing: ethyleneterephthalate as a main constitutional unit; equal to or more than 16mol % and equal to or less than 25 mol % of an aliphatic dicarboxylicacid having 4 to 8 carbon atoms; and equal to or more than 2 mol % andequal to or less than 5 mol % of a metal sulfonate group-containingaromatic dicarboxylic acid.

When the modified polyester fiber has an amount of the copolymerizedaliphatic dicarboxylic acid having 4 to 8 carbon atoms of equal to ormore than 16 mol %, weight reduction tends to be easily performed evenin a range of pH equal to or more than 9 and equal to or less than 13.When the amount of the copolymerized aliphatic dicarboxylic acid having4 to 8 carbon atoms is equal to or less than 25 mol %, thread breakageof said fiber during spinning can be suppressed, and productivitybecomes good.

From the above points of view, it is more preferable that the amount ofthe copolymerized aliphatic dicarboxylic acid having 4 to 8 carbon atomsis equal to or less than 20 mol %.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that the fiber not for weight reductioncontains equal to or more than 50 mass % and equal to or less than 95mass % of synthetic fibers.

When the content of the synthetic fiber in the woven or knitted fabricis equal to or more than 50 mass %, deterioration in the burst strengthof the etching finished part can be suppressed. In addition, when thecontent of the synthetic fiber is equal to or less than 95 mass %, anetched fiber can be contained, and therefore, it becomes possible toexhibit effects of etching finishing easily. From the above points ofview, the content of the synthetic fiber is more preferably equal to ormore than 60 mass % and equal to or less than 80 mass %.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that the synthetic fiber is at least oneof a regular polyester fiber, a polyamide fiber, an elastic fiber, apolyolefin fiber, and an acrylic fiber.

Among the above, from the point of view of strength, the synthetic fiberis preferably a regular polyester fiber, and from the point of view ofexhibiting stretchability, the synthetic fiber is preferably an elasticfiber.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that a single fiber fineness of themodified polyester fiber is equal to or more than 0.6 dtex and equal toor less than 3.5 dtex.

When the single fiber fineness is equal to or more than 0.6 dtex,strength of the woven or knitted fabric can be increased, and when thesingle fiber fineness is equal to or less than 3.5 dtex, etching finishproperties become good, and the texture of the woven or knitted fabrictends to be easily made to be soft.

From the above points of view, it is more preferable that the singlefiber fineness is equal to or more than 0.9 dtex and equal to or lessthan 2.5 dtex.

It is preferable that the woven or knitted fabric according to theinvention is characterized in that the elastic fiber is anyone of apolyurethane fiber, a polytrimethylene terephthalate fiber, and apolybutylene terephthalate fiber, as described above.

It is preferable that the woven or knitted fabric according to theinvention is composed of the modified polyester fiber, the regularpolyester fiber and the polyurethane fiber. When the woven or knittedfabric has the above-described constitution, the woven or knitted fabricwhich has stretchability, high strength, and a soft texture can beobtained.

The method for producing the woven or knitted fabric according to theinvention is a method for producing a woven or knitted fabric, themethod including: printing an etching finish agent on a cloth thatcontains a modified polyester fiber, which is weight reduced under acondition of pH of equal to or more than 8 and equal to or less than 13,and a fiber not for weight reduction; and performing weight reductionprocessing by supplying a superheated steam to a part on which theetching finish agent is printed; the method being characterized in that:the etching finish agent has a pH of equal to or more than 8 and equalto or less than 13; the heating method includes supplying a superheatedsteam of equal to or higher than 150° C. and equal to or lower than 200°C.; and the heating time is equal to or more than 5 minutes and equal toor less than 15 minutes.

The heating method includes supplying a superheated steam of equal to orhigher than 150° C. and equal to or lower than 200° C. onto a part onwhich an etching finish agent is printed. When the temperature of thesuperheated steam is equal to or higher than 150° C., etching finishproperties becomes good, and when the temperature of the superheatedsteam is equal to or lower than 200° C., it becomes possible to preventthe texture of the polyester fiber from becoming hard.

It is preferable that the heating time is equal to or more than 5minutes and equal to or less than 15 minutes.

When the heating time is equal to or more than 5 minutes, etching finishproperties become good, and when the heating time is equal to or lessthan 15 minutes, reduction in strength of the non-etching finished partcan be suppressed.

An etching finish agent is characterized by containing a pasting agentand a component having an etching action in a specific range of pH (pHof equal to or more than 8 and equal to or less than 13) except forguanidine carbonate. It is preferable that the component having theetching action is one or two types selected from sodium carbonate andpotassium carbonate, and it is more preferable that the component havingthe etching action is one type which is sodium carbonate. An amount ofsodium carbonate or potassium carbonate used may be adjusted dependingon the mass of the modified polyester fiber to be etched. In general, itis preferable that the amount of sodium carbonate or potassium carbonateused may be in a range of equal to or more than 5 mass % and equal to orless than 15 mass % to the amount of the etching finish agent. Theetching finish agent may contain an etching finish accelerator,according to the need. The etching finish accelerator is notparticularly limited, and a commercially available etching finishaccelerator may be used. For example, it is preferable that the etchingfinish accelerator is a Mei printer OP-2 manufactured by Meisei ChemicalWorks, Ltd.

Examples of the pasting agent contained in the etching finish agentwhich may be used include a natural pasting agent, a processed pastingagent, a semisynthetic pasting agent, and a synthetic pasting agent.Examples of the pasting agent include a locust bean gum based pastingagent, a starch based pasting agent, a dextrin based pasting agent, acrystal gum based pasting agent, a tragacanth gum based pasting agent, acellulose based pasting agent, carboxymethyl cellulose, polyvinylalcohol, sodium polyacrylate and the like. The pasting agent may be usedalone or two or more types of them may be used. A ratio of the pastingagent is not particularly limited as long as a viscosity suitable forprinting the etching finish agent and performing heat treatment can bemaintained. For example, it is preferable that the pasting agent iscontained in a ratio equal to or more than 1 mass % and equal to or lessthan 10 mass % to the etching finish agent.

The etching finish agent may further contain other compounds such as adye.

A method for etching finishing which includes using the above-describedetching finish agent is described hereinbelow.

The above-described etching finish agent is preferably applied to awoven or knitted fabric containing a modified polyester fiber.

A fiber which is used in combination with the modified polyester fiberis not particularly limited as long as the fiber has a weight reductionresistant property different from the modified polyester fiber. Examplesof the fiber which may be used in combination with the modifiedpolyester fiber include an unmodified polyester fiber (which is composedof an unmodified polyethylene terephthalate, and is also referred to asa regular polyester fiber), a polyamide fiber, a polytrimethyleneterephthalate fiber, a polybutylene terephthalate fiber, a polypropylenefiber, a polyethylene fiber, a polyurethane fiber and the like. Themodified polyester fiber and the above-described fiber are combined byan arbitrary method such as mixed spinning, mixed fiber producing,intertwisting and the like to give a woven or knitted fabric composed ofa yarn, a staple yarn and the like. Then, the woven or knitted fabric issubjected to etching finishing. As the above-described woven or knittedfabric, a fabric which is dyed may be used, according to the need. Dyingis performed by a known arbitrary method on all parts or one part of thefabric by plain dyeing or printing.

Etching finishing may be performed by using the above-described etchingfinish agent, according to a known method which generally includesprinting, heat treating, and washing. In the step of printing, anetching finish agent is printed on a woven or knitted fabric containinga modified polyester fiber in a shape in accordance with a desiredpattern. For printing the etching finish agent, a printing method, aspraying method and the like may be used. The printing method is notparticularly limited, and a frame mold printing method, a flat screenprinting method, a rotary screen printing method, a roller printingmethod and the like may be used. An adhesion amount of the etchingfinish agent onto the woven or knitted fabric may be determinedarbitrarily depending on the printing method, the woven or knittedstructure of the fabric, and the desired pattern.

For example, when the flat screen printing method is employed, aviscosity of the etching finish agent, a hardness of a rubber squeegee,a pressure of a rubber squeegee when printing of the etching finishagent is performed, and a printing speed of a squeegee are determined,depending on the woven or knitted structure to which printing isperformed, a mesh of a flame mold which prints a desired pattern and thelike. Then, the etching finish agent is applied on the fabric in adesired pattern uniformly. In order to confirm that the etching finishagent is uniformly adhered to the fabric, confirmation of whether thereis a blur in a printed part, confirmation of whether there is adifference in a pattern between the right and left of the rubbersqueegee, confirmation of whether the etching finish agent is permeateduniformly into the back surface of the printed part and the likevisually are performed. In addition, a coloring paste which does notcontain an etching finish agent may be printed onto a part other thanthe adhered part of the etching finish agent, in a shape in accordancewith a desired pattern. A method for printing the coloring paste is notparticularly limited, and the same printing method as that of theetching finish agent may be employed. After printing the etching finishagent and the coloring paste to the woven or knitted fabric, the wovenor knitted fabric is appropriately dried, and thereafter, heat treatingis performed.

Examples of the heat treating method include a baking method, a steammethod, a HT steam method and the like. The HT steam method is morepreferably employed.

After the heat treating step, removal of the modified polyester fiberwhich is embrittled on the printed parts, removal of a dye unfixed tothe fiber, which is a dye used in combination with the etching finishagent, and washing of a pasting agent used for a coloring paste which isused for parts other than the adhesion part of the etching finish agent,the dye unfixed to the fiber and the like are performed. A washingmethod is not particularly limited, and washing is performed by a knownmethod. Examples of the washing method include washing with 2 g/L of asurfactant, alkali washing with 2 g/L of a surfactant and 2 g/L of sodaash, acidic washing with 2 g/L of a surfactant and 2 g/L of acetic acid(90%), alkali reduction washing with 2 g/L of a surfactant, 2 g/L ofsoda ash, and 2 g/L of hydrosulfite or thiourea dioxide, and acidicreduction washing with 2 g/L of a surfactant, 2 g/L of acetic acid (90%)and 4 g/L of rongalite. A washing temperature is preferably equal to orhigher than 60° C. and equal to or lower than 100° C., and a washingtime is preferably equal to or more than 5 minutes and equal to or lessthan 30 minutes. After that, washing with water, dehydrating and dryingare performed.

Examples of the surfactant used for washing include a nonionicsurfactant, an anionic surfactant, a cationic surfactant, and anamphoteric surfactant. The surfactant may be used alone or two or moretypes of them may be used in combination.

Examples of the nonionic surfactant include: an ether type nonionicsurfactant such as a higher alcohol alkylene oxide adduct, analkylphenol alkylene oxide adduct, a styrenated alkylphenol alkyleneoxide adduct, a styrenated phenol alkylene oxide adduct, a higheralkylamine alkylene oxide adduct; an ether ester type nonionicsurfactant such as a fatty acid alkylene oxide adduct, a polyalcoholfatty acid ester alkylene oxide adduct, a fatty acid amide alkyleneoxide adduct, and an alkylene oxide adduct of an oil and fat; apolyalkylene glycol type nonionic surfactant such as a polypropyleneglycol ethylene oxide adduct; an ester type nonionic surfactant such asa fatty acid ester of glycerol, a fatty acid ester of pentaerythritol, afatty acid ester of sorbitol, a fatty acid ester of sorbitan, and afatty acid ester of sucrose; other nonionic surfactants such as an alkylether of a polyalcohol, and a fatty acid amide of alkanolamines.Examples of the alkylene oxide include ethylene oxide, propylene oxide,and butylene oxide. A form of an adduct of the alkylene oxide may be arandom adduct of two or more types or may be a block adduct.

Examples of the anionic surfactant include: an anionic surfactant of acarboxylate such as a fatty acid soap; a sulfuric acid ester salt suchas a sulfuric acid ester salt of a higher alcohol, a sulfuric acid estersalt of a higher alcohol alkylene oxide adduct, a sulfuric acid estersalt of a polyoxyalkylene ether, a sulfuric acid ester salt of a phenolalkylene oxide adduct, a sulfuric acid ester salt of an alkylphenolalkylene oxide adduct, a sulfuric acid ester salt of a styrenatedalkylphenol alkylene oxide adduct, a sulfuric acid ester salt of astyrenated phenol alkylene oxide adduct, a sulfuric acid ester salt of apolyalcohol alkylene oxide adduct, a sulfated oil, a sulfated fatty acidester, a sulfated fatty acid, and a sulfated olefin; an anionicsurfactant of a salt of a sulfonic acid ester such as a formalincondensate such as an alkylbenzene sulfonate, an alkylnaphthalenesulfonate, and a naphthalene sulfonic acid, and a sulfonate such as anα-olefin sulfonate, a paraffin sulfonate, and a salt of sulfosuccinatediester; a salt of a phosphoric acid ester such as sodium methyl oleoyltaurate, a salt of a phosphoric acid ester of a higher alcohol, a saltof a phosphoric acid ester of a polyoxyalkylene ether, a salt of aphosphoric acid ester of a phenol alkylene oxide adduct, a salt of aphosphoric acid ester of an alkylphenol alkylene oxide adduct, a salt ofa phosphoric acid ester of a styrenated alkylphenol alkylene oxideadduct, a salt of a phosphoric acid ester of a styrenated phenolalkylene oxide adduct, and a salt of a phosphoric acid ester of apolyalcohol alkylene oxide adduct; and other anionic surfactants such asN-methyltaurine oleate, and N-methyltaurine stearate. Examples of thealkylene oxide include ethylene oxide, propylene oxide, and butyleneoxide. A form of an adduct of the alkylene oxide may be a random adductof two or more types or may be a block adduct. Examples of the saltinclude: an alkali metal salt such as a lithium salt, a sodium salt, anda potassium salt; an ammonium salt, and an amine salt such as a salt ofa primary amine such as a methylamine salt, an ethylamine salt, apropylamine salt, a butylamine salt, and an allylamine salt; a salt of asecondary amine such as a dimethylamine salt, a diethylamine salt, adipropylamine salt, a dibutylamine salt, and a diallylamine salt; a saltof a tertiary amine such as a trimethylamine salt, a triethylamine salt,a tripropylamine salt, and a tributylamine salt; and a salt of analkanolamine such as a monoethanolamine salt, a diethanolamine salt, anda triethanolamine salt.

Examples of the cationic surfactant include a quarternary ammonium saltof an alkyl ether, a quarternary ammonium salt of an alkylamide, aquarternary ammonium salt of a dialkyl ester, a quarternary ammoniumsalt of a dialkyl imidazoline, an alkylamide amine, an alkyl etheramine, an alkylamide guanidine, and an arginine derivative.

Examples of the amphoteric surfactant include an alkylbetaine typesurfactant, an amidopropylbetaine type surfactant, an imidazoliniumbetaine type surfactant and the like.

By the above-described processing method, an etching finished productfrom which the modified polyester fiber in the part where the etchingfinish agent is printed is removed can be obtained. The obtained etchingfinished product is subjected to, according to the need, a knowntreatment such as dyeing and final finishing.

EXAMPLES

The invention is more specifically described hereinbelow by referring toExamples. However, the invention is not limited to these Examples.Meanwhile, methods for measuring and evaluating various characteristicvalues in Examples are as follows.

(Limiting Viscosity [η])

A temperature of a modified polyester was adjusted to 20° C. in a mixedsolvent of phenol/tetrachloroethane=1/1, and a limiting viscosity wasmeasured by the Ubbelohde method.

(Content of Diethyleneglycol (Hereinafter, Abbreviated as DEG))

An obtained modified polyester was subjected to alkaline hydrolysis, andthereafter, each number of moles of ethylene glycol and DEG wasquantified by using a Gas Chromatograph GC-9A manufactured by ShimadzuCorporation, and a content of DEG was obtained as a ratio (%) of thenumber of moles of DEG to the total number of moles of ethylene glycoland DEG.

(Glass Transition Temperature Tg)

A glass transition temperature Tg (° C.) of a modified polyester wasmeasured by using a Differential Scanning Calorimeter DSC 220manufactured by Seiko Instruments Inc., at a temperature raising rate of10° C./min.

(Strength and Elongation)

A strength (cN/dtex) and an elongation (%) were measured according toJIS L1013 by using a tension tester Tensilon UTM-4-100 type manufacturedby ORIENTEC CORPORATION.

(Alkali Weight Reduction Ratio)

A weight reduction ratio of a fiber on which alkali weight reduction wasperformed was calculated as a weight reduction ratio (%) from a mass ofthe fiber before treatment and that of the fiber after treatmentaccording to the following formula:

Weight reduction ratio (%)=((mass of fiber before treatment−mass offiber after treatment)/mass of fiber before treatment)×100.

It is preferable that alkali weight reduction is performed by making afiber to take the form of a knitted fabric from the point of view ofhandleability.

(Burst Strength)

A burst strength was measured according to the Mullen method of JIS L1018.

(Burst Strength Retention Ratio)

Burst strength retention ratio={burst strength of woven or knittedfabric in etching finished part after etching finishing/burst strengthof woven or knitted fabric in non-etching finished part after etchingfinishing}×100(%).

Example 1

To an esterification reaction vessel in whichbis(β-hydroxyethyl)terephthalate and oligomers thereof were present, aslurry of terephthalic acid (hereinafter abbreviated as TPA) andethylene glycol (hereinafter abbreviated as EG) at a molar ratio of1/1.6 was supplied continuously, and an esterification reaction wasperformed under a condition of a temperature of 250° C., a pressure of0.1 Pa, and a residence time of 8 hours. Then, 15.4 kg of the obtainedesterification reaction product was transferred to a polycondensationreaction vessel, and 4.6 kg of an EG dispersion in which a concentrationof adipic acid (hereinafter abbreviated as ADA) was adjusted to 50 mass% was added thereto. In addition, in order to suppress the by-productionof DEG, lithium acetate was added such that a concentration of lithiumacetate was 120 ppm in terms of lithium atom content. After that, themixture was stirred and mixed at a temperature of 230° C. for 5 minutes,and thereafter, as stabilizers, 120 ppm of magnesium acetate in terms ofmagnesium atom content, 140 ppm of triethyl phosphate in terms ofphosphorus atom content and 30 ppm of germanium dioxide in terms ofgermanium atom content were added, and 2.6 kg of an EG solution of5-sodium sulfoisophthalic acid (hereinafter abbreviated as SIP) in whicha concentration of the EG ester of SIP was adjusted to 35 mass % wasadded, and then the mixture was stirred and mixed at a temperature of230° C. Then, as a polycondensation catalyst, 400 ppm of antimonytrioxide was added, and thereafter, the pressure was gradually reducedsuch that the reduced pressure after 60 minutes was equal to or lessthan 1.2 hPa. The mixture was stirred and mixed, and thereafter, thetemperature was raised to a temperature of 270° C., and apolycondensation reaction was performed until a polycondensate reached apredetermined limiting viscosity [η]. As a result, a modified polyesterhaving an amount of the copolymerized ADA of 18 mol %, and an amount ofthe copolymerized SIP of 2.5 mol % was obtained, and the modifiedpolyester was made to be a chip. Polymer physical properties of themodified polyester were shown in Table 1.

The obtained chip of the modified polyester was subjected to spinning byusing a spinning nozzle with a circular shape of a hole and the numberof holes of 24 at a spinning temperature of 255° C., and a spinningspeed of 1,800 m/min. The undrawn yarn was subjected to drawing at adrawing temperature of 65° C., a drawing ratio of 2.28 times, and aratio of a drawing ratio to the maximum drawing ratio (an MDR ratio) of0.72 times. Then, heat setting was performed at 150° C. to give amodified polyester fiber having 84 dtex/24 f (a single yarn fineness of3.5 dtex).

A weft knitted fabric of the modified polyester fiber was produced, and10 g of the knitted fabric was subjected to soaking treatment in 1 L ofan aqueous solution of sodium hydroxide at a concentration of 10 g/L, ata temperature of 98° C. for 20 minutes. Thereafter, the knitted fabricwas subjected to washing with water, dehydrating, and drying. A weightreduction ratio was measured according to the following formula:

Weight reduction ratio (%)={(mass of weft knitted fabric before alkaliweight reduction processing−mass of processed knitted fabric afteralkali weight reduction processing)/mass of weft knitted fabric beforealkali weight reduction processing}×100.

Physical properties of the obtained modified polyester filament yarnwere shown in Table 1.

Example 2

By using the modified polyester chip obtained in Example 1, spinning anddrawing were performed in the same manner as Example 1 except that anamount of a polymer discharged during spinning was changed to 2/5 ofthat in Example 1 to give a modified polyester filament yarn having 33dtex/24 f (a single yarn fineness of 1.38 dtex). Physical properties ofthe obtained modified polyester filament yarn were shown in Table 1.

Example 3

A modified polyester in which 16 mol % of ADA and 2.25 mol % of SIP werecopolymerized was obtained and was made to be a chip in the same manneras Example 1, except that 15.9 kg of the esterification reaction productobtained in Example 1 was transferred to the polycondensation reactionvessel, and an addition amount of the EG dispersion of ADA was changedto 4.1 kg and an addition amount of the EG solution of SIP was changedto 2.4 kg. Polymer physical properties of the modified polyester areshown in Table 1. By using the obtained modified polyester chip,spinning and drawing were performed in the same manner as Example 1except that a spinning speed during spinning was changed to 1,200 m/min.As a result, a modified polyester filament yarn having 84 dtex/24 f (asingle yarn fineness of 3.5 dtex) was obtained. Physical properties ofthe obtained modified polyester filament yarn were shown in Table 1.

Comparative Example 1

A modified polyester in which 14 mol % of ADA and 2.0 mol % of SIP werecopolymerized was obtained and was made to be a chip in the same manneras Example 1, except that 16.4 kg of the esterification reaction productobtained in Example 1 was transferred to the polycondensation reactionvessel, and an addition amount of the EG dispersion of ADA was changedto 3.6 kg and an addition amount of the EG solution of SIP was changedto 2.1 kg. Polymer physical properties of the modified polyester wereshown in Table 1. By using the obtained modified polyester chip,spinning and drawing were performed under a spinning condition and adrawing condition shown in Table 1. As a result, a modified polyesterfilament yarn having 84 dtex/24 f (a single yarn fineness of 3.5 dtex)was obtained. Physical properties of the obtained modified polyesterfilament yarn were shown in Table 1.

Comparative Example 2

A modified polyester in which 10 mol % of ADA and 2.0 mol % of SIP werecopolymerized was obtained and was made to be a chip in the same manneras Example 1, except that 16.9 kg of the esterification reaction productobtained in Example 1 was transferred to the polycondensation reactionvessel, and an addition amount of the EG dispersion of ADA was changedto 2.6 kg and an addition amount of the EG solution of SIP was changedto 2.1 kg. Polymer physical properties of the modified polyester wereshown in Table 1. By using the obtained modified polyester chip,spinning and drawing were performed under a spinning condition and adrawing condition shown in Table 1. As a result, a modified polyesterfilament yarn having 84 dtex/24 f (a single yarn fineness of 3.5 dtex)was obtained. Physical properties of the obtained modified polyesterfilament yarn were shown in Table 1.

Comparative Example 3

A modified polyester in which 5 mol % of ADA and 2.25 mol % of SIP werecopolymerized was obtained and was made to be a chip in the same manneras Example 1, except that 17.6 kg of the esterification reaction productobtained in Example 1 was transferred to the polycondensation reactionvessel, and an addition amount of the EG dispersion of ADA was changedto 1.3 kg and an addition amount of the EG solution of SIP was changedto 2.3 kg. Polymer physical properties of the modified polyester wereshown in Table 1. By using the obtained modified polyester chip,spinning and drawing were performed under a spinning condition and adrawing condition shown in Table 1. As a result, a modified polyesterfilament yarn having 84 dtex/24 f (a single yarn fineness of 3.5 dtex)was obtained.

Said fiber has copolymer components of a polyester fiber which is cationdyeable under normal pressure, which is generally used in the market.

Physical properties of the obtained modified polyester filament yarnwere shown in Table 1.

TABLE 1 Spinning Filament physical properties Copolymer Polymer physicalcondition Drawing condition Single Weight components properties Temper-Tem- Drawing MDR fiber reduction ADA SIP DEG Tg ature Speed peratureratio ratio fineness Strength Elongation ratio mol % mol % % ° C. [η] °C. (m/min) ° C. Times Times dtex cN/dtex % % Example 1 18 2.5 1.24 460.558 255 1800 65 2.28 0.72 3.5 2.43 34.6 22.5 Example 2 18 2.5 1.38 470.565 255 1800 65 2.19 0.72 1.38 2.32 31.2 27.6 Example 3 16 2.25 1.3048 0.562 255 1200 65 2.79 0.75 3.5 2.45 43.4 12.5 Comparative 14 2.01.33 50 0.613 255 1200 75 1.89 0.76 3.5 1.56 32.9 11.7 Example 1Comparative 10 2.0 1.34 56 0.543 270 1200 71 2.34 0.7 3.5 2.02 29.0 7.1Example 2 Comparative 5 2.25 2.40 70 0.544 283 1800 82 2.55 0.71 3.52.99 32.0 6.3 Example 3 *ADA: adipic acid SIP: 5-sodium sulfoisophthalicacid DEG: diethylene glycol

Example 4

48 filaments of a modified polyester fiber having a fineness of 84 dtexwhich was composed of a modified polyester resin obtained bycopolymerizing ethylene terephthalate as a main constitutional unit, 16mol % of ADA and 2.5 mol % of SIP were knitted to give a weft knittedfabric having a Jersey stitch structure.

Alkali weight reduction processing was performed on 100 g of the weftknitted fabric by using a Mini Color dyeing machine (manufactured byTexam Technical Research Institute, Co. Ltd., a multicolor rotation potdyeing test machine), at a concentration of sodium carbonate of 40 g/L,in a mass ratio of the weft knitted fabric to the sodium carbonateaqueous solution of 1:20, at a temperature of the aqueous solution of100° C.×30 minutes. Then, washing with water, dehydrating, and dryingtreatment at 80° C. for 60 minutes were performed to give a processedknitted fabric.

In addition, alkali weight reduction processing was also performed byusing an aqueous solution of each of potassium carbonate, and sodiumhydroxide instead of sodium carbonate in the same manner to give aknitted fabric.

The pH of each of the aqueous solutions, and the weight reduction ratioof each of the modified polyester fibers are shown in Table 2.

Weight reduction ratio (%)=((mass of weft knitted fabric before alkaliweight reduction processing−mass of processed knitted fabric afteralkali weight reduction processing)/mass of weft knitted fabric beforealkali weight reduction processing)×100.

Comparative Example 4

A processed knitted fabric was obtained in the same manner as Example 4except that, as yarns used for the weft knitted fabric, 48 filaments ofa cation dyeable polyester fiber having a fineness of 84 dtex composedof a polyester resin obtained by copolymerizing ethylene terephthalateas a main constitutional unit, 5 mol % of ADA and 2.3 mol % of SIP wereused.

The weight reduction ratio is shown in Table 2.

Comparative Example 5

As yarns used for the weft knitted fabric, yarns composed of apolyethylene terephthalate fiber (an unmodified polyethyleneterephthalate) were used. Hereinafter, the polyethylene terephthalatefiber is also referred to as “a regular polyester fiber”. A processedknitted fabric was obtained in the same manner as Example 4 except thatthe yarns composed of the regular polyester fiber were constituted bythose manufactured by TEIJIN LIMITED, and 36 filaments each having afineness of 84 dtex were used.

The weight reduction ratio is shown in Table 2.

TABLE 2 Weight reduction ratio (%) Sodium Potassium Sodium Copolymercarbonate carbonate hydroxide components 40 g/L 40 g/L 10 g/L ADA SIP pHof aqueous pH of aqueous pH of aqueous Fiber mol % mol % solution = 11.8solution = 11.8 solution = 13.8 Example 4 Modified 16 2.5 9% 8% 39%polyester Comparative Cation 5 2.3 3% 2% 20% Example 4 dyeable polyesterComparative Regular 0 0 0% 0% 1% Example 5 polyester

As shown in Table 2, when alkali weight reduction was performed by usingsodium carbonate, the result was that the modified polyester fiber ofExample 4 had a higher weight reduction ratio than the generally usedcation dyeable polyester fiber of Comparative Example 4, and the regularpolyester fiber of Comparative Example 5 was not capable of being alkaliweight reduced by using sodium carbonate. In addition, when alkaliweight reduction was performed by using potassium carbonate, the resultwas that the modified polyester fiber of Example 4 had a higher weightreduction ratio than the generally used cation dyeable polyester fiberof Comparative Example 4, and the weight reduction ratio of thegenerally used cation dyeable polyester fiber of Comparative Example 4was as low as 2% when being weight reduced by using potassium carbonate,as shown in Table 2. When alkali weight reduction was performed by usingsodium hydroxide, the modified polyester fiber of Example 4 exhibited ahigher weight reduction ratio than the generally used cation dyeablepolyester fiber of Comparative Example 4, and the regular polyesterfiber of Comparative Example 5.

Example 5

Etching finishing which dissolves a modified polyester fiber wasperformed by using a warp knitted fabric obtained by using the modifiedpolyester fiber used in Example 4 and the regular polyester fiber usedin Comparative Example 5 (the modified polyester fiber=16.7%, and theregular polyester fiber=83.4%) and using an etching finish agent havingthe following composition. The composition of the etching finish agentwas shown in Table 3.

-   -   Sorbitose C-5 (10% aqueous solution) (manufactured by AVEBE Co.,        Ltd.) 50 mass %    -   Sodium carbonate (manufactured by Tokuyama Corporation, trade        name: soda ash) 10 mass %    -   Water 40 mass %

A square pattern was printed on the knitted fabric to be treated withthe above-described etching finish agent, and drying at 110° C.×2minutes was performed. Then, a superheated steam treatment was performedby using a HT steamer at 180° C.×8 minutes. After that, washing wasperformed at 80° C.×20 minutes by using a soaping bath containing 2 g/Lof Laccol ISF (manufactured by Meisei Chemical Works, Ltd., a nonionicsurfactant), and thereafter, washing with water, dehydrating, and dryingwere performed to give a processed warp knitted fabric which was etchingfinished.

Evaluation: Etching finish properties were evaluated visually. Asevaluation criteria, as shown in Table 3, with regard to etching finishproperties, when a fiber on which etching is performed in printed partscannot be visually confirmed, the etching finish property was marked by⊙, when etching can be performed though a little residue can beconfirmed visually, and the knitted fabric can be determined as capableof being used as a commercial product, the etching finish property wasmarked by ◯, and when etching cannot be performed and a residue can bevisually confirmed, and the knitted fabric can be determined asincapable of being used as a commercial product, the etching finishproperty was marked by x. In addition, the burst strength in the etchingfinished part was measured according to the Mullen method of JIS L 1018.The results are shown in Table 3. The burst strength of the processedknitted fabric in the non-etching finished part was 755 kPa.

Example 6

An etching finished knitted fabric was obtained in the same manner asExample 5 except that the composition of a paste liquid was changed tothat shown in Table 3, that is, an etching finish accelerator(manufactured by Meisei Chemical Works, Ltd., a Mei printer OP-2) wasused. The evaluation of the etching finish properties is shown in Table3.

By using the etching finish accelerator, etching finish properties whichwere similar to etching finish properties exhibited when a strong alkaliwas used were obtained. On the other hand, deterioration in the burststrength was little.

Comparative Examples 6 and 7

Etching finishing was performed in the same manner as Example 5 exceptthat each composition of the etching finish agents and each ofconditions were changed to those shown in Table 3. Then, the obtainedetching finished knitted fabric was evaluated. The results are shown inTable 3.

Since a strong alkali was used, etching finish properties were good, butdeterioration in the burst strength was large.

TABLE 3 Comparative Comparative Composition of paste liquid Example 5Example 6 Example 6 Example 7 Sorbitose C-5 (10% aqueous solution) 50 5050 50 Sodium carbonate 10 10 Guanidine carbonate 10 Sodium hydroxide 10Etching finish accelerator (Mei printer OP-2) 20 Water 40 20 40 40 pH offinish agent 12.0 12.2 11.8 14.5 Etching finish properties ◯ ⊙ ⊙ ⊙ Burststrength (kPa) 755 628 39 265 Strength retention ratio (%) 94.0 78.0 4.933.0

As shown in Table 3, in Example 5 in which only sodium carbonate wascontained, etching finishing was capable of being performed, andreduction in strength in the etched part was also low. On the otherhand, in Comparative Example 6 in which guanidine carbonate was used aswell as Comparative Example 7 in which sodium hydroxide was used,etching finish properties of the etched parts were good, but extremereduction in strength in the etched parts was observed.

The finish agent which used guanidine carbonate had a pH of 11.8, but itis known that guanidine carbonate becomes a strong alkali when beingheated. Accordingly, deterioration in the burst strength became large.

In addition, in Example 6 in which a Mei printer OP-2, which is anetching finish accelerator, and sodium carbonate were contained, goodetching finish properties were able to be obtained, and reduction instrength in the etched parts was also little.

Example 7

Etching finishing was performed in the same manner as Example 6 exceptthat a knitted fabric (50% modified polyester fiber/50% regularpolyester fiber) obtained by using the modified polyester fiber that isthe same as Example 4 and the regular polyester fiber (manufactured byTEIJIN LIMITED, 84 dtex) that is the same as Comparative Example 5 wasused as a knitted fabric to be treated. Then, an etching finishedknitted fabric was obtained. The evaluation of the etching finishproperties is shown in Table 4. With regard to the evaluation of etchingfinish properties, no fiber was capable of being confirmed visually inprinted parts to which etching was performed, and therefore, theevaluation result was ⊙.

Comparative Examples 8 to 11

An etching finished fabric was obtained in the same manner as Example 5except that the modified polyester fiber used in Example 5 was changedto each of polyester fibers shown in Table 4. The evaluation of theetching finish properties is shown in Table 4.

TABLE 4 Etching finish Fiber for etching properties Example 7 Modifiedpolyester fiber ⊙ Comparative Polyester fiber cation dyeable undernormal pressure X Example 8 (manufactured by KB SEIREN, LTD.)Comparative Polyester fiber cation dyeable under normal pressure XExample 9 (manufactured by MITSUBISHI RAYON CO., LTD.: AHY) ComparativePolyester fiber cation dyeable under high pressure X Example 10(manufactured by Huvis Corp) Comparative Polyester fiber cation dyeableunder high pressure X Example 11 (manufactured by Nan Ya PlasticsCorporation)

INDUSTRIAL APPLICABILITY

According to the invention, it is possible to obtain an etching finishedcloth with good etching finish properties of a modified polyester fiberby using the certain modified polyester fiber as a modified polyesterfiber, without performing alkali weight reduction on a woven or knittedfabric composed of the modified polyester fiber and an unmodifiedpolyester fiber and without causing embrittlement of the unmodifiedpolyester fiber, while removing only the modified polyester fiber inprinted parts. Since no strong alkaline substance which has hightoxicity to human is used, it becomes possible to perform etchingfinishing with high safety in operation.

1: A modified polyester fiber, wherein the modified polyester fiber hasa weight reduction ratio of equal to or more than 5% and equal to orless than 15%, the weight reduction ratio is measured by: adding 100 gof a fiber to 2 L of an aqueous solution including 40 g/L of sodiumcarbonate; heating an obtained mixture at 100° C. for 30 minutes;performing drying treatment at 80° C. for 60 minutes; and measuring afiber mass A g, and the weight reduction ratio is expressed by:weight reduction ratio (%)=((100−A)/100)×100. 2: The modified polyesterfiber according to claim 1, comprising: a modified polyester, whereinthe modified polyester comprises, in a copolymerized form: ethyleneterephthalate; equal to or more than 16 mol % and equal to or less than25 mol % of an aliphatic dicarboxylic acid having 4 to 8 carbon atoms;and equal to or more than 2 mol % and equal to or less than 5 mol % of ametal sulfonate group-containing aromatic dicarboxylic acid. 3: Themodified polyester fiber according to claim 2, wherein the aliphaticdicarboxylic acid is adipic acid, and the metal sulfonategroup-containing aromatic dicarboxylic acid is 5-sodium sulfoisophthalicacid. 4: The modified polyester fiber according to claim 1, wherein themodified polyester fiber comprises equal to or more than 0.5 mass % andequal to or less than 3.0 mass % of diethylene glycol. 5: The modifiedpolyester fiber according to claim 1, wherein the modified polyesterfiber has a single fiber fineness of equal to or more than 0.6 dtex andequal to or less than 3.5 dtex, a fiber strength of equal to or morethan 2.0 cN/dtex and equal to or less than 3.5 cN/dtex, and a fiberelongation of equal to or more than 25% and equal to or less than 45%.6: The modified polyester fiber according to claim 1, wherein themodified polyester fiber comprises lithium acetate at 50 to 120 ppm interms of lithium atom content. 7: A woven or knitted fabric, comprising:equal to or more than 5 mass % and equal to or less than 50 mass % of amodified polyester fiber and equal to or more than 50 mass % and equalto or less than 95 mass % of a fiber not for weight reduction, whereinthe modified polyester fiber has a weight reduction ratio of equal to ormore than 5% and equal to or less than 15%, the fiber not for weightreduction has a weight reduction ratio of equal to or more than 0% andless than 5%; and the weight reduction ratio is measured by: adding 100g of a fiber to 2 L of an aqueous solution including 40 g/L of sodiumcarbonate; heating an obtained mixture at 100° C. for 30 minutes;performing drying treatment at 80° C. for 60 minutes; and measuring afiber mass A g, and the weight reduction ratio is expressed by:weight reduction ratio (%)=((100−A)/100)×100. 8: A woven or knittedfabric, comprising: a modified polyester fiber, and a fiber not forweight reduction, wherein the modified polyester fiber has a weightreduction ratio of equal to or more than 5% and equal to or less than15% and the fiber not for weight reduction has a weight reduction ratioof equal to or more than 0% and less than 5%; the woven or knittedfabric has an etching finished part of the modified polyester fiber; aweight reduction ratio of the modified polyester fiber in the etchingfinished part to the modified polyester fiber in a non-etching finishedpart is equal to or more than 50 mass % and equal to or less than 100mass %; and the weight reduction ratio is measured by adding 100 g of afiber to 2 L of an aqueous solution including 40 g/L of sodiumcarbonate; heating an obtained mixture at 100° C. for 30 minutes;performing drying treatment at 80° C. for 60 minutes; and measuring afiber mass A g, and the weight reduction ratio is expressed by:weight reduction ratio (%)=((100−A)/100)×100. 9: The woven or knittedfabric according to claim 7, wherein a difference between the weightreduction ratio of the modified polyester fiber and the weight reductionratio of the non-etched fiber is equal to or more than 5%. 10: The wovenor knitted fabric according to claim 8, wherein a burst strength of thewoven or knitted fabric in the etching finished part is equal to or morethan 250 kPa and equal to or less than 900 kPa. 11: The woven or knittedfabric according to claim 8, wherein a strength retention ratio of aburst strength of the woven or knitted fabric in the etching finishedpart to a burst strength of the woven or knitted fabric in thenon-etching finished part is equal to or more than 50%. 12: The woven orknitted fabric according to claim 8, wherein the modified polyesterfiber is a modified polyester, comprising, in a copolymerized form:ethylene terephthalate; equal to or more than 16 mol % and equal to orless than 25 mol % of an aliphatic dicarboxylic acid having equal to ormore than 4 and equal to or less than 8 carbon atoms; and equal to ormore than 2 mol % and equal to or less than 5 mol % of a metal sulfonategroup-containing aromatic dicarboxylic acid. 13: The woven or knittedfabric according to claim 8, wherein the fiber not for weight reductioncomprises equal to or more than 50 mass % and equal to or less than 95mass % of synthetic fibers. 14: The woven or knitted fabric according toclaim 13, wherein the synthetic fiber is at least one selected from thegroup consisting of a regular polyester fiber, a polyamide fiber, anelastic fiber, a polyolefin fiber, and an acrylic fiber. 15: The wovenor knitted fabric according to claim 8, wherein a single fiber finenessof the modified polyester fiber is equal to or more than 0.6 dtex andequal to or less than 3.5 dtex. 16: The woven or knitted fabricaccording to claim 14, wherein the elastic fiber is selected from thegroup consisting of a polyurethane fiber, a polytrimethyleneterephthalate fiber, and a polybutylene terephthalate fiber. 17: Amethod for producing a woven or knitted fabric, comprising: printing anetching finish agent on a cloth that contains a modified polyester fiberhaving a weight reduction ratio of equal to or more than 5% and equal toor less than 15% and a fiber not for weight reduction; and performingweight reduction processing by supplying a superheated steam of equal toor higher than 150° C. and equal to or lower than 200° C. for equal toor more than 5 minutes and equal to or less than 15 minutes to a part onwhich the etching finish agent is printed; wherein the etching finishagent has a pH of equal to or more than 8 and equal to or less than 13;and the weight reduction ratio is measured by adding 100 g of a fiber to2 L of an aqueous solution including 40 g/L of sodium carbonate; heatingan obtained mixture at 100° C. for 30 minutes; performing dryingtreatment at 80° C. for 60 minutes; and measuring a fiber mass A g, andthe weight reduction ratio is expressed by:weight reduction ratio (%)=((100−A)/100)×100.